Security features
One of the most important aspects of modern banknotes is of course the security. Without proper security features banknotes could be easily counterfeited. This would make them eventually worthless since the trust of the public is vital to their value. There are loads of security features. I don't even know if the list below is everything (probably not!) but these are some you can find.
- Paper quality
- Crisp sound
- Watermarks
- Security threads
- Matching elements
- Background decorations
- Gradient colouring
- Microtexts
- Kipp effect
- Intaglio printing
- Diffractive Optically Variable Image Device (DOVID)
- Denomination marks
- Serial Numbers
- Anti-copy features
- Optically variable devices
- Metallographics
- Foil
- UV-glowing
- IR-Glowing
- Hair
- Protection ornament
- Marks for the blind
- Polymer banknotes
- Complicated portraits
- STRAP
- Toning
- Microperf
- Shadow image
- Blind embossing
- Clear window
- MVC
- MAGnite
- Durasafe
- EURion constellation
Most banknotes are made from cotton paper with a weight of 80 to 90 grams per square meter. The cotton is sometimes mixed with linen, abaca, or other textile fibres. Generally, the paper used is different from ordinary paper: it is much more resilient, resists wear and tear (the average life of a banknote is 8 months!), and also does not contain the usual agents that make ordinary paper glow slightly under ultraviolet light. Unlike most printing and writing paper, banknote paper is infused with polyvinyl alcohol or gelatin, instead of water, to give it extra strength. Each banknote should have fair resistance to water and wear, at least 2000 folds should be made before torns appear. top^
Especially new banknotes make a specific sound (crisps) when you fold them. This is not the same sound you hear when you fold ordinary paper. top^
Probably the best known security feature in banknotes. A watermark is made by impressing a water-coated metal stamp or dandy roll onto the paper during manufacturing. top^
There are two common types of watermarks: localized, (for instance a portrait) and whole area marks, which cover the entire banknote. Portraits are considered more reliable as a security feature as they contain more semi-shadows. top^
A security thread is a security feature consisting of a thin ribbon that is threaded through the note's paper.Usually, the ribbon runs vertically, and is "woven" into the paper, so that it at some places emerges on the front side and at the remaining places at the rear side of the paper. Usually, it is made of metal foil, but sometimes of plastic. Often, it has some text or numbers (e.g., the denomination) engraved. Threads are embedded within the paper fiber and can be completely invisible or have a star burst effect, where the thread appears to weave in and out of the paper when viewed from one side. However when held up to the light the thread will always appear as a solid line. Features can be built into the thread material e.g., microprinting on a transparent plastic thread or adding materials so they fluoresce under ultraviolet light. The thread is a difficult feature to counterfeit but some counterfeiters have been known to print a thin grey line or a thin line of varnish in the area of the thread. top^
Two different pictures are printed simultaneously on the sides of the banknote. They are parts of one whole sign or symbol. Their location is so precise that when held against the light they form a perfectly matching drawing. This feature is very hard to counterfeit when you make a simple photocopy of a banknote. top^
Background decorations and ornaments usually consist of several "layers", when the next layer is printed over the previous one. The ornament on the layer is usually very small and sometimes simple, but when several layers are combined, they form a very complicated background. top^
Notes are printed with colour gradients that change so slightly that a photocopier would not be able to determine the differences in colour. Even the finest copier will only be able to draw strips of different colours and no soft colour change will ever be seen. top^
Microtext on banknotes is an ever evolving method of an anti-counterfeiting technique that makes printing banknotes on copiers or computer printers an impossible task. The microtext is so small that even the latest computers have extreme difficulty in reaching a quality of print that comes close to the real thing. For those who know what to look for, the areas of micotext on counterfeit notes is typically blurred or reduced to a simple line. The areas of micotext on counterfeit notes is typically blurred or reduced to a simple line. top^
Kipp effect, or the latent image, is a relatively new feature added to the banknotes beginning with the 1980ies. It's made with the help of intaglio printing. Usually the image is "hidden" in the areas of the same tone and it's built of raised parallel lines, which are perpendicular to the raised lines of the background. When you rotate such area with the light reflecting from it, at certain angles you will see the picture appearing and then changing into negative. top^
"Intaglio" means "raised". It's developed by placing about 60 layers of paint on the same place on the note and to apply pressure of about 60 tons in weight. The letters (or drawings) thus acquire volume and you can feel them with your fingers. At the same time it's applied so strongly that you can't scratch the paint off. More info on this process can be read here. top^
Diffractive Optically Variable Image Device (DOVID)
A group of anticoping devices that are based on the phenomenon of light diffraction (Hologram, Kinegram, Gyrogram etc.). Holograms and kinegrams are some of the most advanced security features today. Holograms usually show a volumetric image, while kinegram changes colours when a viewpoint is changed. Impossible to be reproduced without extremely expensive equipment, they gain more and more popularity. As usual, the kinegrams incorporate the denomination of the banknote, while holograms depict portraits. DOVID's are usually used in a form of patch or strip stamped to paper. top^
On most banknotes the denomination is written several times in numerals of different sizes in different locations on the banknote. A common way of counterfeiting lesser known banknotes is by increasing the number of zeroes on the note to change it's face value. To prevent this, the denomination is repeated in many more ways, like in the microtext, backgrounds and in words (or combined). top^
Each banknote's number is unique, and they never repeat in a series. There are several number formats used in the world: some numbers have series in letters while some haven't, some numbers may include 5 digits while others may have 10. The way of writing a number can be a security feature too. The numerals can be increasing in size or decreasing. The numbers are usually repeated twice on a banknote. top^
Anti-copy features are for instance drawn lines and decorations which make the banknote impossible to be copied without the help of specialized copying equipment. The edges of such blocks of lines have different distances between the lines, and when attempting to copy the banknote, these edges appear as dark and displaced areas which show that you see a copy of the note, not the original. top^
This a group of security devices that display shift of colour or become visible when observed at different angles. There are three different variations:
1. optically variable ink (OVI): ink that displays shift of colour when observed at different angles.
2. iridescent ink: ink that displays a rainbow effect when observed at different angles.
3. optical security device (OSD): a reflective film composed of very thin layers of metallic and ceramic materials that changes colour when observed at different angles. top^
Many modern banknotes have so called "metal dust" on them. It's is a paint which has small metal particles in it that give the banknotes a unique metal glitter where applied. It's used for many purposes, sometimes in combination with other features. top^
Their are two different uses for foil in a banknote. One is foil plating and the other is foil stamping.
1. Foil plating is the incorporation of small pieces of foil into the banknote paper which glitter from the paper. It's not easy to counterfeit this feature.
2. Foil stamping is the incorporation of a metallized film or foil stamped to the paper with an overprinted image or text. The example on the right is a foil stamp. top^
An image printed with special ink that becomes visible when observed in ultraviolet light. top^
An image printed with ink containing special particles that are being activated by infrared light and after that become visible. top^
"Hair" are small pieces of specially treated materials (silk as usual) added to the banknote paper when it's being made. Their task is to act as an additional security feature as they glow with a different colour when being lighted by UV. The amount of such "hair" can be different from note to note and they have no fixed location. top^
Protection ornaments are used to prevent counterfeiters add extra zeros to the denomination. This happened for instance in Georgia, when coupon banknotes were introduced. In 6 months so many "corrected" banknotes appeared that the government had to issue new notes with this kind of security feature. top^
Marks for the blind are closely involved with intaglio printing as they are what the blind people can feel with their fingertips. Depending on the denomination, the picture will differ. However, there's a more advanced way like a note made in Canada. Canadian banknotes have magnetic marks (viewed as black marks on the reverse, see picture) and when installed in a special small reading machine, a voice tells the denomination. top^
Polymer banknotes are the most advanced banknotes. Furthermore plastic is far more resistant to wear than paper, it doesn't dissolve in water and doesn't burn. The average life term of polymer note is several years (unlike the 8 months of a paper note). Besides, some security features of the polymer notes are unique - like the transparent windows. top^
Portraits are perhaps the hardest thing to counterfeit in the banknotes. All other details may have geometric proportions or may be much easier to reproduce than the human face. The more details the portrait has, the more difficult it is to draw. Portraits can be combined with other security features like intaglio printing and UV-glowing. Take a look at the portrait from Lithuanian 5 litai banknote (click to enlarge) to see how many details it consists of. top^
STRAP = System of Transparent Reflection Against Photocoping. It is a wide polymer strip with alternated metallized and demetallized areas. When a banknote is copied using a photocopier the copy looks totally different from the original because of this strip. It's quite an expensive feature to incorporate in a banknote so it's not widely used. top^
Paper toning is one of the most widely spread security features. The idea is to make the banknote paper have it's own unique colour tone. And the more delicate the tone is, the more difficulty it is to reproduce. The additional bonus of such feature is that it's easier to distinguish the banknotes of different values by colour than by any other properties. top^
An image made of numerous microholes in paper that becomes visible in transmitting light. top^
An image that's visible when a banknote is observed in transmitting light. It is used on polymer banknotes only as a analogue of watermark on paper. top^
Colourless relief printing. An image made by this technique becomes visible at an oblique angle. For an example, click here. top^
A transparent area of a banknote. The window can have blind embossing image or posses some optical properties. It is used on polymer banknotes only. top^
MVC stands for 'Moire Variable Color'. A rainbow effect that appears on a monochromic field when a banknote is tilted. For an example, click here. top^
A new security feature that has just been developed and hasn't been incorporated in any banknote yet. It consists of a pigment that allows reversible changes between two colour states. The alignment of the pigments and the colours perceived can be controlled externally simply with magnetic effects. So in other words: when you hold a magnet to the paint, the colour will shift. You can read more about this new feature in this post. top^
This is a new paper-polymer-paper composite produced by Fortress Paper at the Landqartmill. It´s first use is in the 25 Dirhams note from Morocco. Read more about this new 'paper' in this post. top^
Tiny dots which were invented by the Japanese Omron Corporation. They consist of a pattern of five small circles, which is repeated across areas of the banknote at different orientations. Photocopiers can recognize these patterns and will give a warning or even refuse to copy the banknote. The security feature is widely used on banknotes like the euro, the US dollar and many others. top^
